Surface-Emitting Laser Current Bypass for Low-Resistance Reflection
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Solution Overview
Problem
Current surface-emitting laser devices face challenges in reducing the resistance value between the substrate and the semiconductor layer, leading to inefficiencies in light emission and increased photoabsorption due to high-resistance reflection layers.
Innovation Solution
The introduction of a bypass wiring that forms a current path detouring the high-resistance reflection layer, electrically connected to the clad layer in the first removal portion and the substrate in the second removal portion, reduces the overall resistance and minimizes photoabsorption by using a low-concentration or impurity-free reflection layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-resistance reflection layer is used to reflect light, then light reflection efficiency is improved, but electrical resistance increases causing higher forward voltage and reduced device performance
Solution Approach 1:
The device is divided into two separate functional layers: a reflection layer for optical function and a clad layer for electrical function. The reflection layer (InP-based) provides high reflectivity without requiring high resistance, while the clad layer (AlGaInAs-based) provides the necessary electrical confinement and low resistance current blocking, separating optical and electrical functions to resolve the contradiction.
Solution Approach 2:
Different regions of the device are assigned different material properties optimized for their specific functions. The reflection layer uses InP-based materials with high optical reflectivity, while the clad layer uses AlGaInAs-based materials with high electrical resistance and low optical absorption, allowing each layer to excel at its designated function without compromise.
2Reliability
If the resistance value between substrate and semiconductor layer is reduced to improve current flow, then electrical conductivity is improved, but light emission efficiency decreases due to increased photoabsorption
Solution Approach 1:
The current path is segmented to flow through the low-resistance clad layer rather than through high-resistance reflection layers. The clad layer provides a dedicated electrical conduction path with minimal optical absorption, separating current transport from optical interaction to simultaneously achieve low resistance and high light emission efficiency.
Solution Approach 2:
The clad layer acts as an intermediary between the substrate and the active region, providing both electrical current blocking and optical transparency. It mediates between the electrical requirements (low resistance current path) and optical requirements (minimal absorption), allowing current to flow efficiently while light passes through with minimal loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves the forward voltage characteristic and enhances the performance of the surface-emitting laser device by reducing resistance and photoabsorption, leading to more efficient light emission.
Implementation Method 1
a first reflection layer 13 made of a compound semiconductor... the first reflection layer 13 has a refractive index, which periodically changes in the normal direction Z... reflects light having a specific frequency
Implementation Method 2
an active layer 11... laminated on the first clad layer 14... generates light when current flows through the semiconductor structure
Data Source
AI summary
A surface-emitting laser device includes a first-conductivity type substrate including a first main surface on one side and a second main surface on an opposite side, a first-conductivity type reflection layer laminated on the first main surface so as to be lower in concentration than the substrate, a first-conductivity type clad layer laminated on the reflection layer so as to be higher in concentration than the reflection layer, an active layer laminated on the clad layer, a second-conductivity type semiconductor layer laminated on the active layer, a first removal portion that is formed by digging down the semiconductor layer and the active layer so as to expose the clad layer and that demarcates a mesa structure having a plateau shape, a second removal portion that is formed by digging down the clad layer and the reflection layer from a bottom portion of the first removal portion so as to expose the substrate from a position distant from the mesa structure, and a bypass wiring that is electrically connected to the clad layer in the first removal portion and that is electrically connected to the substrate in the second removal portion.